More than 1,700 fishing boats raced out of Nova Scotia ports before first light Tuesday morning on what is known as Dumping Day – the opening of Canada’s biggest and most lucrative lobster fishery.

It also signals the start of when their U.S. rivals in Maine and Massachusetts will begin to feel the sting of the 8 percent tariff differential created when Canada signed a new trade deal with Europe, leaving American lobstermen to wonder just how much of that valuable market they are about to lose.

During their last six-month season, the two inshore fishing territories off the southwestern coast of Nova Scotia, labeled No. 33 and 34 out of Canada’s 45 lobster zones, landed about 33,500 metric tons of lobster that raked in about $493 million in Canadian dollars. To get a sense of scope, the 1,500-boat fleet between Halifax and Digby caught as much lobster during its half-year run as Maine fishermen did in all of 2016.